1. Field of the Invention
The present invention generally relates to an input device, and more particularly to the input device for transmitting input information by a radio communication.
2. Description of the Related Art
In the current computer system industry, in order to simplify connections to peripheral devices and to improve operability thereof, a wireless communication has been applied to the peripheral devices such as a mouse and a like.
As a wireless communication method, a radio wave method and an infrared ray method have developed. The radio wave method is applied to a coordinate input device such as the mouse because of a wider flexible range of an input position thereof.
In the coordinate input device applying the wireless method, if there is a conductive object around the coordinate input device, an electrostatic capacity (load capacity), which is occurred between the object and the mouse, is applied to an antenna of the mouse. Then, a transmission rate becomes lower. If a radio field intensity of the mouse is set to be stronger and exceeds a predetermined level so that the transmission rate will not be lower, it is required to get a permission in accordance with the radio wave law. Accordingly, in general, the radio field intensity is set to be at a maximum while not requiring the permission in accordance with the Wireless Telegraph Law.
In a conventional input device applying a radio communication, the antenna is formed on a circuit board arranged on a bottom surface of a housing of the mouse. Therefore, for example, when the mouse is operated on a desk made from steel material, an antenna effect is degraded. And an area, in which the radio field intensity output from the input device is degraded, locally occurs.